A photo-voltaic cell or pv cell or solar cell is a semi-conductor device that converts light energy directly into electrical energy by the means of photo-voltaic effect. Individual photo-voltaic cell is are connected either in series or parallel or both to create solar panel of desired voltage and current i.e it is the building blocks of solar panels. Almost all the photo-voltaic cells available in market is consists of crystalline silicon.
Construction of Photo-voltaic cell
A photo-voltaic cell is consists of several layers of materials each with a specific purpose. The most important layer of a photo-voltaic cell is semiconductor layer which consists of two distinct layers of p-type and n-type semiconductor.
A layer of conductor is placed on both the sides of the semiconductor layer. The backside or shaded side of the cell can have completely covered with the conductor layer whereas the front or illuminated side have sparingly conductor layer. One or several layer of anti-reflection coating is applied to the illuminated side of the photo-voltaic cell.
Working of Photo-voltaic cell
When sunlight falls on photo-voltaic cell, it interacts with the material present inside the cell. The photons in sunlight are absorbed by the semiconductors materials causing the atoms of the semiconductors to release electrons creating electron-hole pairs.
The electric field created due to pn-junction of the cell separates the electron-hole pairs i.e it pulls the electrons towards n-type semiconductor layer and holes towards p-type semiconductor layer. The conductor placed on the front of the cell collects negative charges i.e electrons whereas the conductor placed on back collects positive charges i.e holes.
This collected charges flow as the electric current when the photo-voltaic cell is connected to an external circuit.
Efficiency of Photo-Voltaic Cell
The efficiency of a photo-voltaic cell is the amount of electrical energy coming out of the cell compared to the energy of the sunlight falling on it. The efficiency of a pv cell depends on the types of semiconductor material and the technology used for manufacturing it. The maximum theoretical efficiency of a pv cell is around 33% or 0.33 and this is referred to as shockley-queisser limit.
Advantages of photo-Voltaic Cell
- The environmental effects of photo-voltaic system is minimal as it generate clean, sustainable, renewable and green energy source as no any harmful gases like COX, NOX, e.t.c are emitted.
- Low operation and maintenance cost as sunlight is freely available and abundant.
- Solar panels are also available in remote areas or sparsely inhabited areas, cheaper than conventional power transmission line.
Disadvantages of Photo-Voltaic Cell
- Efficiency of photo-voltaic cell is low compared to other renewable energy sources.
- Energy from the sun can only be harnessed only in presence of sunlight.
- High installation cost.
- It is fragile i.e can be damaged easily.
- As it generates dc power so long transmission is difficult.
Applications of Photo-Voltaic Cell
- In vehicles
- In calculators and wristwatches
- In space explorations
- In experiments
- Solar power plants
- Residential areas
- Industrial areas
- Agriculture sector
- As photo-detector